Many, solid oxides, such as stabilized zirconia, behave like semi-conductors except that instead of conducting electrons, they conduct oxygen ions. Previously used tubular and flat plate cell geometry arrangements for removing oxygen from oxygen-containing gas, or for pumping substantially pure oxygen streams, have had very uneven oxygen removal distributions or oxygen pumping efficiencies, due to electrical current mal-distribution over the cell. This has resulted in excessive solid electrolyte requirements and excessive power consumption. Moreover, there, has been a tendency to damage the solid electrolyte due to over depletion of the oxygen-containing gas stream.